Hydraulic control system

ABSTRACT

A tractor includes an engine, a transmission coupled to the engine, a hydraulic pump driven by the engine, at least one of a tractor implement, attachment, or control moved by the hydraulic pump, a sensor, and a controller coupled to the transmission. The controller is configured to downshift the transmission based on a signal from the sensor.

BACKGROUND

The present disclosure relates to a hydraulic control system for avehicle, in particular for a tractor.

Tractors often include hydraulic control systems that utilize ahydraulic pump to generate a flow of hydraulic fluid for control and tooperate tractor implements (e.g., front shovel, rear shovel, mowingblades, planter, etc.). The hydraulic pump is driven by an engine of thetractor.

When a load from a tractor implement is not taxing the engine, thetractor typically benefits from a shift-up, throttle-back (SUTB)condition. With a higher gear ratio of the transmission, lower enginespeed can achieve a required ground speed. Slower gears, shafts andother rotating components generally provide improved fluid economy. TheSUTB condition may be adequate for the tractor when the tractor isplanting or carrying out another operation as it traverses across afield. The hydraulic flow needs of the pump are met by the lower enginespeed and are dictated by power requirements and available pumpdisplacement. At the end of a field row or other condition requiringadditional hydraulic fluid flow, however (e.g., when a planter needs tobe hydraulically raised or when a tractor implement otherwise begins totax the engine), the SUTB condition may not provide enough pump speed ata maximum displacement to meet hydraulic needs. Current systems do notchange the gear ratios of the transmission in this situation. Inparticular, the controls of current systems do not recognize unmethydraulic flow needs and the available pump displacement that couldsatisfy those needs.

SUMMARY

In another aspect, the disclosure provides a tractor having an engine, atransmission coupled to the engine, a hydraulic pump driven by theengine, at least one tractor implement, attachment, or control moved bythe hydraulic pump, a sensor, and a controller coupled to thetransmission. The controller is configured to downshift the transmissionbased on a signal from the sensor.

In one aspect, the disclosure provides a swashplate pump assembly havinga swashplate pump with a pump housing and a swashplate disposed withinthe pump housing. The swashplate pump assembly also includes a sensorconfigured to detect an angle of the swashplate.

In another aspect, the disclosure provides a control system foradjusting a transmission on a tractor. The control system includes amemory and a processor. The processor is configured to receive a firstsignal from a sensor and to determine whether a hydraulic pump isapproaching a maximum pump displacement based on current engine speedfrom the first signal. The processor is further configured to send asecond signal to a transmission to cause the transmission to downshiftand the engine to speed up if the processor determines that thehydraulic pump is approaching the maximum pump displacement.

Other aspects of the disclosure will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a hydraulic control system.

FIG. 2 is a schematic illustration of a hydraulic pump of the controlsystem.

FIG. 3 is a flowchart illustrating use of the hydraulic control system.

DETAILED DESCRIPTION

Before constructions of the disclosure are explained in detail, it is tobe understood that the disclosure is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the accompanyingdrawings. The disclosure is capable of supporting other constructionsand of being practiced or of being carried out in various ways.

FIG. 1 schematically illustrates a tractor 10 and a hydraulic controlsystem 14 disposed therein. While the hydraulic control system 14 isdescribed in the context of the tractor 10, the hydraulic control system14 may be utilized with any other motorized vehicle, including but notlimited to agricultural or industrial vehicles, or with any machineswith fluid flow needs, variable displacement hydraulics, and powermanagement automation.

As illustrated in FIG. 1, the hydraulic control system 14 includes anengine 18. The engine 18 is a diesel engine, although in otherconstructions the engine 18 may be an internal combustion engine,electric motor, etc. The engine 18 is coupled to a transmission 22. Thetransmission 22 is an automatic transmission controlled by a controller24 (which may include a memory and a processor for receiving and sendingsignals and performing calculations), although in other constructionsthe transmission 22 is a manual transmission.

With reference to FIGS. 1 and 2, the hydraulic control system 14 furtherincludes a hydraulic pump 26 coupled to and driven by the engine 18. Thehydraulic pump 26 is a variable displacement pump that supplieshydraulic fluid to power and move one or more tractor implements,attachments, or controls 30 (e.g., on-board control such as steering, aplanter, front shovel, rear shovel, mowing blades, etc.).

In the illustrated construction the hydraulic pump 26 includes a pumphousing 34, a swashplate 38 disposed inside of the pump housing 34, andpiston cylinders 40 disposed inside of the pump housing 30 that arepressed (e.g., via a spring or other biasing element) against theswashplate 38. The housing 34, swashplate 38, and piston cylinders 40may be conventional. The available pump displacement of the hydraulicpump 26 is determined based on an angle 41 of the swashplate 38 withinthe pump housing 34. For example, the angle of the swashplate 38 isvariably adjustable to any angle between two fixed angles, a first fixedangle corresponding to a minimum pump displacement, and a second fixedangle corresponding to a maximum pump displacement (each of the firstand second angles being measured for example relative to an axis of thehousing or any other reference line or plane as is understood in thefield of swashplate pumps). In some constructions the angle of theswashplate 38 may be adjusted manually or automatically via a lever,hydraulic cylinder, spring, or other structure.

With reference to FIG. 1, the hydraulic control system 14 furtherincludes a sensor 42 to detect an angle of the swashplate 38. In theillustrated construction the sensor 42 is a Hall Effect swivel anglesensor, although other constructions may include various other types ofsensors 42 (e.g., rotary potentiometers, etc.), any of which may be usedto detect an angle of the swashplate 38 within the pump housing 34. Inthe illustrated construction the sensor 42 is disposed within the pumphousing 34. In other constructions the sensor 42 is spaced from the pumphousing 34, and the pump housing 34 includes an opening or openingsthrough which the sensor 42 may view or otherwise detect the angle ofthe swashplate 38. In some constructions multiple sensors 42 are used todetect the angle of the swashplate 38, As illustrated in FIG. 1, thesensor 42 (or sensors 42) is in communication with (e.g., wirelessly)the controller 24.

FIG. 3 illustrates a control process 46 for operating the hydrauliccontrol system 14. At block 50 of the control process 46, the sensor 42initially monitors the angle of the swashplate 38, and sends a signal tothe controller 24. In some constructions the sensor 42 is programmed orotherwise directed to continuously monitor the angle and providesignals. In other constructions the sensor 42 intermittently monitorsthe angle of the swashplate 38, or monitors the angle only upon acommand from an operator.

At block 54 of the control process 46, the controller 24 receives asignal from the sensor 42 and determines an angle of the swashplate 38.If the controller 24 determines that the angle of the swashplate 38 isincreasing and has reached a predetermined percentage (e.g., 85%, 90%,95%, etc.) of its second fixed angle, or has reached a predeterminedangle close to that of the second fixed angle (i.e., indicating that thepump 26 is approaching its maximum pump displacement based on currentengine speed), the controller 24 sends a signal to the transmission 22and engine 18 to automatically downshift the engine 18 and increaseengine speed (assuming increased engine speed is available).

In some constructions, the controller 24 utilizes the followinglogic/code, where “maximum hydraulic pump displacement” corresponds tothe predetermined percentage or predetermined angle referenced above:

If current hydraulic pump displacement=maximum hydraulic pumpdisplacement and (engine speed<(rated engine speed or operator setmaximum engine speed)), then

-   -   Downshift    -   Increase engine speed    -   Set state to pump flow control drive strategy=true

Downshifting and increasing the engine speed increases the availablepump displacement capacity for the pump 26. While downshifting maydecrease the fluid economy and/or increase the noise of the tractor 10and the engine 18, the tractor 10 will at least be able to meet itshydraulic fluid needs during the temporary period. Thus, duringconditions where extra hydraulic fluid flow is needed (e.g., at the endof the row in the field when the tractor 10 wishes to lift a planter orduring other temporary conditions where extra hydraulic fluid pressureis needed for the tractor implement, attachment, and/or control 30, or asystem of tractor implements, attachments, and/or controls 30), thetransmission 22 in the hydraulic control system 14 will deviate from thestandard SUTB condition.

By initiating the downshift prior to the swashplate 38 reaching itssecond fixed angle (e.g., at 85%, 90%, 95%, etc. of the second fixedangle), the transmission 22 has enough time to complete the downshiftbefore the swashplate 38 has reached the second fixed angle and the pump26 has reached its maximum displacement based on current engine speed.In some constructions the transmission 22 may complete the downshiftsimultaneous to the swashplate 38 reaching the second fixed angle. Theangle of the swashplate 38 at which the downshift is triggered may bedependent upon the particular tractor 10 or other vehicle and the timeduration required for downshifting for that particular vehicle.

In some constructions, and with continued reference to block 54 in FIG.3, the controller 24 determines whether a single gear shift or multiplegear shifts are required to meet the hydraulic fluid needs of the pump26. For example, if significant added hydraulic pressure is needed, thecontroller 24 may determine that multiple downshifts are needed, andwill thus cause the transmission 22 to downshift more than once or skipgears. This innovation also works with transmission types of aninfinitely variable nature wherein gear step size is very small. Changesof transmission ratio, engine speed and pump displacement may occur morefrequently in smaller steps.

The benefits of this logic/code are an enhanced output of the hydrauliccontrol system 14 and an increased capability to reduce losses throughuse of SUTB whenever possible. Additionally, pump sizing can be kept toa minimum. In some constructions, when the pump 26 demands engine speedshigher than peak power of the engine 18, the peak power value can beused to limit supplemental hydraulic flow. This is a hydraulic powerversus absolute engine power compromise situation.

While the illustrated construction utilizes a swashplate pistonhydraulic pump, in some constructions the hydraulic pump 26 is a fixedpump with a variable displacement motor on the tractor implement,attachment, or control 30. In yet other constructions the hydraulic pump26 is a vane pump, or other type of variable-displacement pump.Additionally, while the illustrated construction uses a sensor 42 todetect an angle of a swashplate 38, in yet other constructions thesensor 42 may be a flow meter that detects displacement of the pump 26.So long as a displacement or flow can be measured at the pump 26 via thesensor 42, the controller 24 is then able to identify that the pump 26is approaching its maximum displacement or flow, and can accordinglydownshift the engine and/or increase engine speed.

For example, in constructions where the sensor 42 is a flow meter, theflow meter may be calibrated to the pump 26. The controller 24 may thengather information (e.g., from the sensor 42 and/or other sensors) onflow, pump input speed and any volumetric efficiency and temperaturecompensation relationships. The controller 24 may then solve therelationships provided below to determine pump displacement as comparedto the pump's possible displacement range:

PumpFlow=PumpSpeed×PumpDisplacement×VolumetricEfficiency

PumpDisplacement=PumpFlow/(PumpSpeed×VolumetricEfficiency)

1×RPM×(1×cm³/REV)×92%=9.2×10⁻⁴ (liter/min)

In some constructions, volumetric efficiency may be a function of oiltemperature. Calculated displacement may be compared to minimum andmaximum displacement of the pump 26 and may be used as an equivalent toa swashplate angle measurement.

With continued reference to FIG. 3, and as illustrated in block 58, insome constructions once the angle of the swashplate 38 has decreased andfallen back below the predetermined percentage of the second fixed angle(or below the predetermined angle), the controller 24 receives a signalfrom the sensor 42 indicating the decreasing angle and causes thetransmission 22 to shift back up. In some constructions, the controller24 may determine whether a gear shift up will satisfy hydraulic pumpflow needs. The controller 24 may utilize the following logic/code:

If (maximum hydraulic pump displacement−current hydraulic pumpdisplacement−margin)/maximum hydraulic pump displacement>gear step size,then

-   -   Revert to normal drive strategy SUTB control    -   Set state to pump flow control drive strategy=false

In some constructions, and as noted above, the transmission 22 may be amanual transmission. Thus, in these constructions the sensor 42 providesa signal to the operator (e.g., to a display, or an audio signal) thatthe angle of the swashplate 38 is closely approaching the second fixedangle. The operator may then manually downshift the transmission 22 soas to increase engine speed. In these constructions the angle of theswashplate 38 at which the signal is provided may be different than thatof the automatic transmission 22, so that the operator has enough timeto manually downshift before the swashplate 38 reaches the second fixedangle. Additionally, the sensor 42 may provide a signal to the operatorthat the angle of the swashplate 38 has fallen below the predeterminedpercentage. The operator may then manually up-shift.

Various features and advantages of the disclosure are set forth in thefollowing claims.

What is claimed is:
 1. A tractor comprising: an engine; a transmissioncoupled to the engine; a hydraulic pump driven by the engine; at leastone of a tractor implement, attachment, or control movable by thehydraulic pump; a sensor configured to detect an angle of a swashplatein the hydraulic pump; and a controller coupled to the transmission,wherein the controller is configured to downshift the transmission basedon a signal received from the sensor.
 2. The tractor of claim 1, whereinthe hydraulic pump includes a pump housing and wherein the swashplate isdisposed within the pump housing.
 3. The tractor of claim 1, wherein thesignal received from the sensor corresponds to the angle of theswashplate.
 4. The tractor of claim 3, wherein the transmission is anautomatic transmission, wherein the signal is a first signal, andwherein the controller is configured to send a second signal to theautomatic transmission and engine.
 5. The tractor of claim 4, whereinthe controller is configured to determine whether the swashplate hasreached a predetermined angle based on the first signal, and wherein thecontroller is configured to send the second signal to the automatictransmission if the swashplate has reached the predetermined angle. 6.The tractor of claim 5, wherein the second signal is configured to causethe automatic transmission to downshift.
 7. The tractor of claim 1,wherein the at least one of a tractor implement, attachment, or controlis one of a planter on-board control, a front shovel, a rear shovel, ora mowing blade.
 8. A swashplate pump assembly comprising: a swashplatepump having a pump housing and a swashplate disposed within the pumphousing; and a sensor disposed within the housing and configured todetect an angle of the swashplate.
 9. The swashplate pump assembly ofclaim 8, wherein the swashplate pump is a hydraulic pump disposed withina tractor.
 10. The swashplate pump assembly of claim 9, wherein theswashplate pump is coupled to at least one of a tractor implement,attachment, or control, and wherein the swashplate pump is configured tosupply hydraulic fluid to cause movement of the tractor implement,attachment, or control.
 11. The swashplate pump assembly of claim 8,further comprising a controller coupled to the sensor, wherein thecontroller is configured to receive a signal from the sensorcorresponding to the angle of the swashplate.
 12. The swashplate pumpassembly of claim 11, further comprising an automatic transmission,wherein the signal is a first signal, and wherein the controller isconfigured to send a second signal to the automatic transmission. 13.The swashplate pump assembly of claim 12, wherein the controller isconfigured to determine whether the swashplate has reached apredetermined angle based on the first signal, and wherein thecontroller is configured to send the second signal to the automatictransmission if the swashplate has reached the predetermined angle. 14.The swashplate pump assembly of claim 13, wherein the second signal isconfigured to cause the automatic transmission to downshift.
 15. Acontrol system for adjusting a transmission on a tractor, the controlsystem comprising: a memory; and a processor, wherein the processor isconfigured to receive a first signal from a sensor and to determinewhether a hydraulic pump is approaching a maximum pump displacementbased on the first signal, wherein the processor is further configuredto send a second signal to a transmission to cause the transmission todownshift if the processor determines that the hydraulic pump isapproaching the maximum pump displacement.
 16. The control system ofclaim 15, wherein the sensor is configured to determine an angle of aswashplate within the hydraulic pump.
 17. The control system of claim16, wherein the processor is configured to send the second signal if theprocessor determines that the angle of the swashplate has increased to apredetermined angle.
 18. The control system of claim 15, wherein theprocessor is configured to send a third signal to the transmission ifthe processor determines that the angle of the swashplate has fallenbelow the predetermined angle.
 19. The control system of claim 18,wherein the third signal is configured to cause the transmission toupshift.
 20. A tractor having the control system of claim 15, whereinthe tractor includes an engine coupled to the transmission and at leastone of a tractor implement, attachment, or control coupled to thehydraulic pump.